Little is known about the genetic programs responsible for cell fate decisions, particularly concerning the mechanisms by which progenitor information is passed to daughter cells. Using the developing retina as a model system, cDNA microarrays will be used to determine the gene expression profiles of retinal progenitor cells. These experiments will be done using two complementary approaches. The first utilizes a Chxl0GFP BAC transgenic mouse generated in our laboratory. This mouse allows for the sorting out of retinal progenitor cell populations that can be profiled on our retinal cDNA microarrays. Additionally, single retinal progenitor cells will be isolated and profiled using the same cDNA microarrays. These two approaches will allow for the identification of many novel genes, including transcription factors and signaling molecules, involved in retinal progenitor cell biology. Also, the single cell approach will allow for the establishment of the number of distinct gene expression patterns and, therefore, a determination of the number of retinal progenitor cell subsets that exist. In diseases such as retinoblastoma, the transformed target cell population is completely unknown and the analysis proposed here should be instrumental in discovering it. [unreadable] [unreadable]